The present invention generally relates to green roof systems, also known as roof landscaping systems, living roof systems, and roof gardens, suitable for supporting live plant growth on building roofs. More particularly, the present invention relates to modular green roof systems and related methods of use.
Green roofs are typically found in non-arid environments or require irrigation to thrive. In hot/arid climates, water is often a limiting resource in green roof systems both because of limited total precipitation and increased evaporation from solar loading. Frequently, conventional green roof systems fail to retain adequate amounts of water. This inadequate retention of water can result in increased storm water runoff, which can adversely contribute to flooding, and which can result in less than optimal growing media water retention. Failure to retain water in the green roof system also limits the amount of water that can be efficiently transpired from the system over time.
A green roof is a roof of a building that is partially or completely covered with vegetation and soil, or a growing medium, usually planted over a waterproofing membrane. This does not refer to roofs which are merely colored green, as with green roof shingles. Benefits of green roof systems are numerous. For one, green roofs provide increased aesthetics due to the presence of flowers and other foliage. Green roof systems can be a source of fruits and vegetables as well. Additionally, green roof systems are generally beneficial from an energy conservation standpoint due to the improved insulation they provide. For example, green roof systems reduce heat loss during the winter months by adding additional insulation and thermal mass. They are, in fact, quite effective in reducing cooling loads during the summer, through shading the roof surface, and the evaporative cooling effects from evapotranspiration of plants and soils. In this way, green roof systems may reduce energy consumption and save costs through lower energy bills. Moreover, in addition to providing an energy savings benefit, insulation from green roof systems can provide an additional sound insulation benefit as well.
Green roof systems are also known to reduce ambient urban temperatures in the vicinity of the buildings on which they are installed. This effect, also known as the “urban heat island effect” can be rather dramatic, with some studies showing a decrease of up to 34° C. for roof top temperatures. In addition to a reduction of roof top temperatures, green roof systems are known to minimize diurnal temperature fluctuations of underlying roof structures. Green roof systems benefit the environment through multiple mechanisms, including by filtering pollutants and carbon dioxide out of the air and by filtering pollutants and heavy metals out of rainwater.
In some instances, green roof systems may be required or encouraged by local regulations or green roofs may ease compliance with local regulatory requirements, particularly with respect to storm water runoff requirements. By reducing storm water runoff, flooding and pressure on municipal stormwater systems may be reduced. In some cases, installation of green roof systems reduce required government fees.
Further, green roof systems have been known to increase the life span of a roof of up to 2-3 times, resulting in a lower lifetime cost and lower maintenance costs.
Nevertheless, numerous challenges are faced by conventional green roof systems. For example, many conventional green roof systems are heavily stressed by arid to semi-arid climates, due to high rates of water loss through evaporation from solar loading, often removing much of the plant-available water from the growing medium. Mulching is one method of preventing evaporation loss from the substrate by the addition of another layer of porous material on top of the substrate. Stone and gravel mulches are quite heavy, making them unsuitable for use in green roof systems. Organic mulch decomposes too quickly in hot climates and is also unsuitable for long-term use in green roof systems.
Often, conventional green roof systems are susceptible to damage from the conditions to which they are exposed, including high winds, hail, and overland surface flow of water. These conditions result in the loss of growing media, disturbance to the vegetative root zone, and in extreme conditions, sediment entrainment into wind currents can result in projectile damage to surrounding objects. Those green roof systems able to support sufficient vegetative or structural protection are often too heavy for many roofing applications, particularly retrofit applications where roofs are not built to handle significant additional loads.
Accordingly, improved green roof systems are needed to address one or more disadvantages of the prior art.